The present application relates generally to a process for converting paint-saturated alkaline earth metal carbonates into a reusable material. In particular, a process is provided for re-milling paint-saturated alkaline earth metal carbonates obtained from overspray paint systems that are suitable for use in the manufacture of products not requiring a pure, bright white calcium carbonate.
Alkaline earth metal carbonates, such as calcium carbonates, are used as particulate filter media in a variety of industrial processes. For example, alkaline earth metal carbonates recently have been employed as a filter aid to capture paint booth overspray, such as during the spray painting of new automobiles. See e.g., U.S. Pat. Nos. 7,959,722 and 8,241,406.
In such paint overspray systems, the alkaline earth metal carbonates typically are fluidized so as to thoroughly mix with and adsorb paint overspray particles. Because of the high surface area of the particulate alkaline earth metal carbonates, the individual paint particles wet the surfaces of the alkaline earth metal carbonates and form agglomerates of the paint-saturated alkaline earth metal carbonates, in turn reducing the effective surface area of the alkaline earth metal carbonates and preventing proper fluidization. The paint-saturated alkaline earth metal carbonates then are captured for disposal, which currently is limited to landfills (both alone and as an absorbent for hazardous liquids) or use as a fill material in concrete and cement-based materials.
Accordingly, there is a need for a simple process that converts paint-saturated alkaline earth metal carbonates into a form that can be beneficially reused in various applications, particularly applications in which recycled materials are desired.